Skip to main content

Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

See other formats


VARIEGATED, ORANGE AND BUTLER GLACIERS
123
Outside of the black moraine was a broad area of clear ice, which in time may give rise to a small interior flat, though possibly, as ablation proceeds, a sufficient amount of incorporated debris will be concentrated on the surface to prevent this. Beyond the area of clear ice, at the very edge of the broken portion of the glacier, and on its front, which rises above the interior flat, was a veneer of reddish orange moraine. This was apparently a mass of the old moraine cover pushed forward and mixed-up, at least such of it as has not been incorporated in the ice. All semblance of the former banding of moraine had disappeared and the only extensive morainic area in the broken portion of the glacier was this reddish orange moraine which covered the front of the inner bulb and a narrow strip back of it,a total width of  to ^ mile of moraine-veneered ice, where in 1905 there were two miles or more of banded moraine.
Excepting at the front of the bulb, near the ulterior flat, the moramic veneer was very
Russe/lfiorJ
'te (fed Black Interior FaM Red Purple Granite Rusted Gneiss F/ff Whlfe Hforylne Moraine Moraine MwSnc Moraine                  Moraine
Grttn Morafnf
tfonfinf
Russell Fiona
mite    Red   Black    Interior Granlli KusteJ Gneiss    Ffot Moraine Mmine Moraine
Otrfy     /c Crevasssd
RussellFtord
>ifr'l.viH*^^'^-i i J-j  tt-i n ".'Ti'ljV.m.'.l'At  11_ i -fl   J_ i    Y-*   -I       Lr '   * *f        T I  PT  .   '
White   Red    Bhck   Interior Red. Orange and   Clean Ice \ ffntnlfe Rusted Gneiss   f/at     Vtiri<igafe<f?(ora/ne                    S
C/ean fee
Moraine Mtrgint Mor&lne
FIG. 8.   LONGITUDINAL SECTIONS OF VABIBQATBD GLACTEB.
thin and unstable. Ablation was still rapidly in progress, even in the morainic area, but the debris cover was becoming thick enough and, over large areas, general enough so that the future rate of ablation will be materially checked.
Aside from the sudden advance, sudden cessation of the advance, and subsequent rapid ablation, one of the most notable features is the development of the black moraine (Fig. 8), apparently the result in part of the re-establishment of contact with the black hornblende portals to the mountain valley, in part to the outward movement of the black hornblende lateral moraine that before 1906 had developed in the marginal gully at the mouth of the mountain valley. In earlier days, when the glacier was in contact with these walls, its currents carried the de*bris out far enough to give rise to the great crescent that forms the outer wall of the interior flat next Hubbard Glacier; but by the spasmodic rush of 1906, which again established contact with the black hornblende slopes, the forward advance was so soon ended that the black moraine could not be earned out nearly so far. It lies a mile or more from the crescent on the outer margin, of the flat. Had the ice advance continued, and the glacier spread out in a broader bulb,